1. Field of the Invention
The present invention relates to a magnetic head that a magnetic path is formed by magnetic metal films.
2. Description of the Related Art
For example, in a magnetic recording/reproducing apparatus such as a video tape recorder, digital recording for recording by digitalizing a signal is progressed for improving image quality.
With improvement on high density of magnetic recording and high frequency of recording frequency, a magnetic head mounted on the magnetic recording/reproducing apparatus must exhibit high output and a little noise in a high frequency area. For example, in the compound-metal-in-gap type magnetic head that a magnetic metal film is formed on ferrite materials and a coil is wound which is used often for a conventional magnetic head for VTR, inductance is large and output per inductance drops, therefore, the output is low in the high frequency area and it is hard to correspond sufficiently to digital image recording that high frequency and density is necessary.
Therefore, the thin film type magnetic head manufactured by a thin film forming process is examined as the magnetic head corresponding to the high frequency.
The thin film type magnetic head is formed by joining a pair of magnetic head half members having magnetic metal films through a gap material. The magnetic metal films are buried into the magnetic head half members, the joined surface includes nonmagnetic materials such as glass and an almost rectangular concave part for forming a coil is provided almost at the center. Further, the magnetic head half members have a coil (not shown) formed by the thin film forming method such as photo lithography in a concave part for forming the coil. A magnetic gap is formed between the magnetic metal films by joining a pair of magnetic head half members through a gap material including of a nonmagnetic substance.
Magnetic metal films 100A and 100B which the magnetic head half members include, as shown in FIG. 1, form a magnetic core 101 that is a magnetic path in the thin film magnetic head by joining a pair of magnetic head half members. A concave part 102 is formed at the magnetic metal films 100A and 100B and the concave part 102 forms the concave part for forming the coil as above mentioned. These magnetic metal films 100A and 100B, for example, in case of being used as the magnetic head for 8 mm, are that the magnetic core 101 as shown by A in FIG. 1 is about 200 micrometers wide and a medium siding part as shown by B in FIG. 1 is about 50 micrometers wide. The width A of the magnetic core 101 is regulated by depending on the width of the whole form of the magnetic head.
The width B of the medium sliding part is formed comparatively small for controlling the contact width with a medium. Therefore, when a pair of magnetic metal films 100A and 100B are joined, the magnetic core 101 is formed almost convex that an opening part 103 is in the neighborhood of the center.
Thus, the thin film type magnetic head is formed as the width B regulated by thickness of the medium sliding part of the magnetic core 101 is smaller than the width A regulated by the thickness of the magnetic head. Therefore, the magnetic head keeps good contact with the magnetic recording medium and maintains good magnetic resistance.
When a signal magnetic field is reproduced or recorded to the magnetic recording medium in the conventional thin film magnetic head, the magnetic core 101 formed by joining the magnetic metal films 100A and 100B is the magnetic path. That is to say, the magnetic field generated by the coil formed in the concave part for forming the coil or the signal magnetic field generated by the magnetic recording medium magnetizes the magnetic core 101 formed by joining the magnetic metal films 100A and 100B.
Further, the conventional thin film type magnetic head is formed as the width A regulated by the thickness of the magnetic head is larger than the width B regulated by thickness of the medium sliding part. Therefore, in the thin film type magnetic head, as shown in FIG. 2, form of the magnetic core 101 that is a magnetic path is almost convex. Further, in the thin film magnetic head, as above mentioned, the concave part for forming the coil is formed. Therefore, in the thin film magnetic head, an opening part 103 is almost at the center of the magnetic core formed almost convex.
In the conventional thin film type magnetic head, when the magnetic core 101 is almost formed convex, cross section of each part of the magnetic core 101 is different. Further, in the thin film type magnetic head, when the cross section of each part of the magnetic core 101 is different, magnetic resistance is changed according to change of the cross section. That is to say, in the thin film type magnetic head, as shown by R in FIG. 2, the magnetic resistance becomes sharply large at the part where the cross section becomes sharply small.
Generally, in the magnetic head, it is considered that when the magnetic resistance becomes gradually larger from the part on which the coil is wound to the magnetic gap, electromagnetic conversion efficiency is good. However, in the thin film magnetic head, the magnetic resistance sharply becomes large at an area R as above mentioned. Therefore, in the conventional thin film type magnetic head, there was a problem that the electromagnetic conversion efficiency dropped.